Commercial alumina templates as base to fabricate 123-type high-T_c superconductor nanowires

Nanowires of high-T_c superconductors of the RE-123 type (RE = rare earths) were grown by the anodized alumina template method, employing commercially available alumina templates with nominal pore diameters of 20 and 100 nm. Pre-reacted YBa₂Cu₃O_x (YBCO) and NdBa₂Cu₃O_x (NdBCO) powder was molten on top of the templates in order to fill the pores with the 123-type material. The resulting samples were oxygen-annealed at 450 °C. Superconductivity with a transition temperature of 88 K (YBCO) and 96 K (NdBCO) was confirmed by means of magnetic susceptibility measurements (SQUID) using pieces of the filled template. The electric (resistance) and magnetic measurements revealed further relatively sharp superconducting transitions. To understand the dimensions of the resulting nanowires (length up to 10 μm, diameter between 100 and 250 nm), which do not correspond to the nominal pore diameters, the empty and filled commercial templates were analyzed in detail by scanning electron microscopy. We discuss the feasibility of this approach to produce larger amounts of nanowires.